Many studies have been conducted on recording systems using capsules, and many systems, such as pressure-sensitive recording systems and heat-sensitive recording systems have so far been developed.
The art teaches various embodiments described, for example, in U.S. Pat. Nos. 2,712,507, 2,730,456, 2,730,457, 3,418,250, 3,432,327, etc. In the prior arts, there is a disadvantage that record responding to light as is in the present invention has not been made, although record responding to pressure and heat has been made.
Attempts have also been made to prepare recording materials using capsules whose capsule wall is made of a light-sensitive high polymer. However, as is well known, since the thickness of a capsule wall is as thin as not more than 100 .mu.m, and yet some wall strength is essentially necessary, recording materials which utilize change in capsule wall strength caused by crosslinking reaction fundamentally involve difficult problems.
Japanese Patent Application (OPI) Nos. 124343/82 and 88739/83 (the term "OPI" as used herein means an "unexamined published application") describe microcapsules containing a photocurable composition which comprises a vinyl compound and a photopolymerization initiator. These relate to recording materials utilizing differences in the curing degree caused by imagewise exposure, to thereby cure microcapsules in exposed areas. However, such microcapsules have the defect that they are susceptible to pressure, to form fog during storage with time before being exposed, i.e., in a non-cured state.
Furthermore, U.S. Pat. No. 4,551,407 discloses microcapsules containing a composition which comprises a photo-decomposable polymer. The microcapsules basically utilize a change in viscosity of the internal phase, caused by decomposition of the polymer contained in the microcapsules in exposed areas through imagewise exposure. In this case, however, pressure fog occurring during storage before use is not satisfactorily prevented.